The present invention relates, in general, to the control of electricity to the lights on a boat trailer and, more particularly, to apparatus for automatically disconnecting the electrical circuits on a boat trailer from the corresponding circuits on a towing vehicle when the trailer is placed in a body of water during launching and reloading of a water craft.
When a boat is being towed to and from a launching area, highway safety laws require the boat trailer to be provided with running lights, brake lights, and turn signal indicators. These lights are energized by connecting them to corresponding electrical circuitry on the towing vehicle. In order to launch or reload the boat on the trailer, the trailer is typically backed down an inclined ramp into the body of water, thereby permitting the flotation properties of the boat to make boat launching and boat reloading a relatively easy task. As a result, a substantial portion of the trailer's lighting system is submerged for a period of time. If the electrical system on the trailer has not been disconnected before the trailer is submerged, the light bulbs on the boat trailer which are or become energized during submersion are likely to break because of contrasting temperatures between the bulb and the water and the electrolytic effect of submerging both poles of the bulb in a conductive medium. There is also a possibility that if several light bulbs break, the current draw will be sufficient to blow the fuse as well. In order to prevent the foregoing from occurring, boaters typically disconnect the trailer's electrical circuitry before backing the trailer into the water. Physical disconnection is a frequently overlooked task, particularly when others are waiting to use the launch ramp.
The foregoing problem was addressed in U.S. Pat. No. 4,620,109 (Kummer) which discloses an electrical circuit for disconnecting the lights on a boat trailer from those on the towing vehicle. The circuitry disclosed in the foregoing patent requires the operator to turn on the headlights on the towing vehicle and shift it into reverse in order to disconnect the trailer lights and, upon withdrawing the trailer from the water, to turn off the headlights on the towing vehicle for a brief instant in order to reactivate the trailer lights. The foregoing approach has several disadvantages. First, it requires the operator to take certain steps which are no easier to remember than the earlier practice of disconnecting the electrical coupling between the trailer and the car. Secondly, the driver of the towing vehicle may unknowingly de-energize the trailer lighting system during normal driving conditions. If the trailer is being towed at night or at other times when the towing vehicle's lights are on and the towing vehicle is shifted into reverse (for instance, to back out of a parking space), the trailer will lose all of its lights. Likewise, if the driver of the towing vehicle forgets to turn off the vehicle's headlights for a brief instant after pulling the trailer from the water, the lighting system on the trailer will not become re-energized. Third, if the operator failed to provide enough time for water to drain out of the trailer light housings before switching the headlights off, the trailer lights would be reactivated while a destructive water environment was still present. Thus, the present inventor was faced with the problem of devising a reliable and relatively inexpensive circuit capable of automatically disabling the trailer lighting circuitry as the trailer was entering a body of water and then automatically re-energizing the trailer lights after sufficient time had elapsed for water to drain out of the trailer light housings upon emerging from the boat ramp.